This article will take an in-depth look at shock, bungee, and elastic cords.
The article will bring more detail on topics such as:
This chapter will cover bungee cords, shock cords, elastic cords, and their production processes.
A bungee cord, also referred to as a shock cord or elastic cord, consists of multiple elastic strands encased in a woven fabric. It features hooks at both ends for attachment and secure fastening.
Typically made from rubber and encased in a fabric cover, the bungee cord's elastic properties make it versatile for various uses. It is often employed to secure luggage or cargo on the exterior of vehicles.
The elastic strands of the bungee cord are made of rubber, can be natural, synthetic, or even a configuration of both. It’s all dependent on the use of a bungee cord. The outer woven sheath can be made of any material such as polypropylene, cotton, or nylon. These materials are helpful in protecting the outer sheath and provide an extra stretch to the cord.
Bungee cords are primarily made from rubber, which can be either synthetic or natural. Natural rubber, or latex rubber, is often preferred due to its high tensile strength and excellent elasticity, allowing it to return to its original shape. These characteristics make natural rubber an ideal choice for bungee cords. However, latex rubber has limited resistance to sunlight and air, meaning that ultraviolet radiation can cause degradation over time.
Synthetic rubber, such as neoprene, offers better resistance to sunlight and air compared to natural rubber. However, it generally has lower tensile strength and flexibility. Consequently, natural rubber is often preferred for applications requiring military specifications and for activities like bungee jumping due to its superior performance characteristics.
The outer coating of a bungee cord is typically made from braided fabric, such as cotton or nylon yarn. The type of fabric used depends on the intended application of the cord. Commercially used bungee cords usually have a single layer of nylon, which provides enhanced abrasion resistance and high tensile strength. In contrast, bungee cords designed for military use or bungee jumping often feature a double layer of cotton for added durability. Additionally, some specialized bungee cords are covered with a braided natural rubber layer.
The design specifications of bungee ropes vary depending on their intended use. Commercial bungee ropes typically come in diameters ranging from 0.25 inches to 0.62 inches. For military applications, the diameter can range from 0.25 inches to 0.87 inches. Bungee cords specifically designed for jumping generally have a diameter of 0.62 inches.
Bungee cords are engineered to stretch to specific lengths and elongation percentages. The elongation of a bungee cord is measured by how much it stretches compared to its original, unstretched length. For instance, if a bungee cord extends to twice its initial length, it is considered to have an elongation of 100%.
The production of bungee cord involves the following steps:
The initial stage in manufacturing bungee cord involves extracting either natural or synthetic rubber, which is then formed into long ribbons. These rubber ribbons typically measure between 0.09 and 0.12 inches in thickness, 0.25 inches in width, and can be up to 100 feet long. The rubber ribbons are fed into an extruder, a heated cylinder with two openings. The rubber is pushed through the extruder under pressure and emerges from a smaller opening shaped to the desired form. Following extrusion, the rubber undergoes a cooling process before being sent to manufacturers for further use.
The tensile strength and diameter of a bungee rope are influenced by the number of strands and ribbons incorporated into the cord. During the braiding process, these strands are evenly unwound from their coils. In hot weather, there is a risk that the strands may stick together. To prevent this, the rubber strands are coated with a fine layer of talc or soapstone. This coating is applied continuously throughout the unwinding process.
The next stage involves braiding the rubber strands using a machine known as a braider. The free ends of the rubber strands are manually inserted into the braider, where they are gently pressed by rollers and other mechanisms. On the output side, another roller or take-up reel pulls the strands through the machine.
During this process, the rubber strands are kept under tension and slightly stretched by adjusting the speed and pressure. This stretching reduces the diameter of the strands and ensures a tight wrap of the fabric covering. As the strands pass through the braider, yarn is woven around them to form the cover. It is crucial that this covering is tightly woven to prevent dirt from entering the yarn gaps when the cord is fully extended. If multiple yarn layers are required, they are applied sequentially. Additionally, the outer yarn covering can be colored or color-coded according to the client’s specifications.
When the bungee cord is manufactured, it is ready to be shipped. The cord is cut to the required length, coiled and then placed in a cardboard box. These cords are also placed in dark plastic bags to protect them from sunlight, air, and ultraviolet radiation.
The manufacturer does not attach end fittings to the bungee cord during production; these are added based on specific requirements. For bungee cords used for securing luggage and equipment, the cord is first cut to the desired length. Both ends are then doubled and coiled with stiff wire using a wire coiler machine. After coiling, a J-shaped hook is affixed to secure the ends. In contrast, bungee cords intended for jumping are tightly wrapped with a strong, waxed string called whipping. The ends are bent around a non-metallic eye, and in some cases, the cord is sewn onto woven fabric webbing.
Quality control of bungee cords depends on several factors, which should be verified using the following methods:
Visual inspection involves examining the cord for any visible defects, such as imperfections in the rubber, incorrect coloring, gaps in the woven sheath, or any broken sections of the cord.
Testing the bungee cord is crucial for assessing its tensile strength, load capacity, and extension rate. This should be performed for all types of bungee cords, whether for commercial or military use. These properties can be evaluated by applying various loads to the cord and measuring its performance.
Some companies produce their own bungee cords and apply specific colors for various purposes. Military bungee cords, however, come in designated colors that indicate their manufacturing date. These cords tend to lose efficiency over time, so it is recommended to use them within six months of manufacture. Colors such as green, yellow, red, and blue are assigned based on the manufacturing date and are subject to periodic updates. In contrast, the colors used for commercial bungee cords are primarily for aesthetic purposes.
A shock cord is constructed with a high-quality rubber core and a polyester cover, making it compact, durable, and stable. Shock cords are versatile and can be used for various applications, including securing tools to a harness and fastening gear.
The outer cover of shock cords is made from highly abrasion-resistant polyester, which effectively protects the inner rubber core. While shock cords are similar to bungee cords in many aspects, they typically do not come with a hook like bungee cords. Shock cords are also utilized in military applications to absorb impacts from large cargo, parachutes, and in bungee jumping activities.
Features of shock cords include:
Elastic cords have a smaller diameter compared to shock or bungee cords. They are ideal for use in smaller projects, such as creating jewelry like necklaces and bracelets. Additionally, elastic cords are commonly used to make headbands, lanyards, and decorative items for classrooms, dorm rooms, or living spaces.
While smaller shock cords are available, larger versions are suitable for securing tarps, tents, and items in the bed of a trailer or truck. However, depending on the load and height of the transported items, a shock cord might not always be ideal for securing larger loads. Both shock cords and elastic cords are versatile and can be used in various DIY projects, including organizing kitchen utensils, bundling toys, and securing items like bikes in a garage.
While both elastic cords and shock cords are made from similar materials, shock cords generally offer greater stretch or elongation compared to elastic cords. Typically, a shock cord can elongate up to 100%, meaning it can stretch to twice its original length. In contrast, elastic cords usually elongate up to 50%, stretching to one and a half times their original length.
This chapter will explore the various types of bungee cords, shock cords, and elastic cords.
The different types of bungee cords, also known as shock cords, include:
These bungee cords feature adjustable lengths to suit various applications. Typically, they can extend up to 32 inches (including the hook) and can be adjusted to a minimum length of 10 inches. This adjustability makes them ideal for household and light-duty tasks.
Adjustable bungee cords are designed with lighter tension compared to heavy-duty variants, allowing them to stretch easily for various tasks. Typically, they have a thickness of 8 mm and feature metal hooks at both ends, which are coated to prevent scratches. These bungee cords are cost-effective and versatile, making them suitable for everyday uses such as household storage, securing gear, and attaching items to hiking backpacks.
These bungee cords are equipped with a comfortable plastic finger grip for safe handling. The design ensures that the cord stays securely in place while stretching, addressing a common safety concern associated with bungee cords.
These bungee cords feature sturdy metal hooks with plastic coatings to prevent scratches. They typically come in lengths ranging from 32 to 48 inches. Made from a UV-resistant latex blend and cross-woven rubber, these cords are designed to resist thinning or brittleness over time. They are durable and suitable for both indoor and outdoor use across various climates. For convenient storage and portability, the cords come with a zippered carrying case.
These bungee cords are available in lengths from 7 to 70 inches. They feature a high-quality rubber core encased in an abrasion-resistant cover for extended durability. The hooks are adjustable and reinforced with fiber for added strength.
The hooks are also UV stabilized and include a finger grip for safe handling. The hooks have a patented locking design that is easy to adjust. To adjust the hooks, no ties, knots, or mechanical ratchets are required; they are just slid to the length desired, and then the cord is pulled to lock it into position. The length can also be changed while the bungee cord is in use. These types of bungee cords are suitable for application indoors or outdoors.
These bungee cords are designed to endure challenging conditions. They are wrapped in a high-grade Dacron polyester sheath for enhanced durability.
The sheath of these bungee cords is resistant to ultraviolet radiation, moisture, oils, chemicals, and abrasion. Made from Dacron polyester, a synthetic fiber known for its low stretch and high strength, the sheathing ensures the cord performs well during extended outdoor use. These cords meet established safety standards.
These bungee cords feature a premium-grade rubber core for durability and longevity. The woven outer sheath is UV-resistant, making it suitable for outdoor use and repeated exposure. Typically available in 10-inch lengths, they come with dichromate steel hooks that resist warping under tension. Additionally, these cords are offered in a variety of bright and vibrant colors.
These bungee cords offer both visibility and functionality, making them ideal for various household tasks. They are commonly used indoors for organizing and securing items, such as in a workshop or garage. Their UV resistance also makes them suitable for outdoor use, including applications like securing tarps, camping gear, and more.
These bungee cords come equipped with two steel carabiner hooks featuring a wide-mouth design. These hooks are significantly stronger than standard bungee cord hooks, providing a more secure attachment.
The hook and latches are kept in place by the spring loaded closure, once attached. This functions to prevent the accidental release of the hooks, making this bungee cord a particularly safe pick. The base of the hook features a molded grip, which increases strength and security to the user. These types of bungee cords come in 48 inch lengths and are designed to withstand ultra violet rays and weather damage. They are composed of premium rubber that remains elastic for repeated use. These types of bungee cords are used for home, recreational, and work use when a reliable hook is required.
The types of elastic cords include:
This cord features an elastic core and is coated with polyester available in a range of colors. It is ideal for making visible hair accessories and other designs where the cord's appearance is important. However, this type of cord is not suitable for creating durable jewelry.
This type of elastic cord is available in various colors but offers limited size options, typically 0.5mm and 0.7mm, which are ideal for smaller beads. Unlike Stretch Magic, Stretch Floss is made from multiple strands of elastic material woven together, enhancing its elasticity and making it easier to knot compared to single-strand cords.
This widely used elastic cord is rubbery, round, and composed of a single strand, making it well-suited for large beads. While Stretch Magic can be a bit more challenging to knot securely compared to other elastic cords, it remains a reliable choice. To ensure a tight hold, it is recommended to use a surgeon's knot with an additional half knot.
This chapter will cover the various uses and benefits of bungee, shock, and elastic cords.
Here are some practical applications for bungee cords:
Bungee cords can be employed to hang canning rings, offering a neat and accessible storage solution. This method is preferable to stashing them away in a dark drawer, as it keeps them visible and easy to retrieve.
For a temporary paper towel holder, short bungee cords can be utilized. Simply thread the cord through the roll and secure it by hooking both ends to sturdy fixtures. This setup is ideal for keeping paper towels within reach while camping or during outdoor events.
Bungee cords can also serve as a convenient strap for carrying mats. Place the cord along the mat's center, then pull both ends around the mat and hook them to secure the rolled-up mat, creating an easy-to-carry handle.
To entertain a baby during a road trip, bungee cords can be used to hang their favorite toys. Stretch the cord between the handles in the back seat and hang the toys from it, creating a mobile that keeps them entertained throughout the journey.
To avoid grocery spills in the car, use a bungee cord to secure the bags. Thread the cord through the handles of each bag and then fasten it around the headrest of the car seat where the groceries are placed, preventing spills even over bumps.
To keep trash bags from slipping down into garbage cans, wrap a bungee cord around the rim of the can after positioning the bag. Hook the cord to itself to ensure the bag stays in place.
For wire shelving, bungee cords can be used to create a barrier across the front edge. This prevents items from falling off the shelf and allows you to maximize storage without worrying about items toppling over.
A bungee cord can provide an easy way to add an extra layer to your curtains without needing additional hardware. Simply thread the bungee cord through the top of the curtain and hook each end onto the curtain rod. This method allows you to easily install a layer of blackout curtains behind your existing ones, effectively blocking more light in a bedroom.
To maximize space in the kitchen, you can store baking sheets vertically using bungee cords. By stretching a few bungee cords vertically between shelves, you create a simple storage solution. The baking sheets can then be slid between the cords, keeping them organized and saving valuable space.
Despite their drawbacks, the benefits of bungee, shock, and elastic cords far outweigh the disadvantages.
Bungee cords, shock cords, and elastic cords may be constructed from the same materials but have differences in their elasticity and applications. Bungee cords are more suitable for outdoor use in which great strength is required, whereas elastic cords cannot withstand too much tension. Shock cords are not suited for applications requiring great strength. They do suit applications that require medium strength compared to bungee and elastic cords. Elastic cords have a small diameter and are best suitable for small crafts such as jewelry making. Lastly it is important to make careful considerations when purchasing bungee, shock, or elastic cords.
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